A phosphopantetheinyl transferase homolog is essential for Photorhabdus luminescens to support growth and reproduction of the entomopathogenic nematode Heterorhabditis bacteriophora

fThe bacterium Photohabdus luminescens is a symbiont of the entomopathogeni c nematode Heterorhabditis bacteriophora. The nematode requires the bacteri um for infection of insect larvae and as a substrate for growth and reprodu ction. The nematodes do not grow and reproduce in insect hosts or on artifi cial media in the absence of viable P. luminescens cells. In an effort to i dentify bacterial factors that are required for nematode growth and reprodu ction, transposon-induced mutants of P. luminescens were screened for the l oss of the ability to support growth and reproduction of H. bacteriophora n ematodes. One mutant, NGR209, consistently failed to support nematode growt h and reproduction, This mutant was also defective in the production of sid erophore and antibiotic activities, The transposon was inserted into an ope n reading frame homologous to Escherichia coli EntD, a 4'-phosphopantethein yl (Ppant) transferase, which is required for the biosynthesis of the catec hol siderophore enterobactin. Ppant transferases catalyze the transfer of t he Ppant moiety from coenzyme A to a holo-acyl, -aryl, or -peptidyl carrier protein(s) required for the biosynthesis of fatty acids, polyketides, or n onribosomal peptides, Possible roles of a Ppant transferase in the ability of P. luminescens to support nematode growth and reproduction are discussed .